This invention relates to a pump impeller for pumping a coolant and particularly for a water pump for cooling an internal combustion engine.
Water pumps for internal combustion engines are well known and are present in the larger internal combustion engines. A widely used water pump generally includes an impeller mounted within a housing. The impeller includes a plurality of spaced vanes secured on a round base. The impeller is secured to a drive shaft and is rotatably mounted within the walls of a pump housing. The housing includes an outer closure wall and a shroud over the outer ends of the impeller vanes. A one-piece fully enclosed and double shrouded impeller has been disclosed. However, the system of manufacture is expensive and involves a complex procedure requiring a special high maintenance die unit with a timed and multiple pull action such as found in a camera shutter. An alternative common impeller is a two-piece assembly in which a separate shroud is attached to the vanes of the impeller by a separate means, such as chemical bonding, sonic welding, or a mechanical connection. A one piece impeller with an integral shroud has been disclosed with a special arrangement and location of the shroud.
The water pumps for internal combustion engines generally operate in a high temperature environment. A seal unit is mounted with a bearing to the shaft at the base of the impeller. Cooling of the seal unit at the connection of the impeller shaft to the pump is significant. This requires special construction of the pump unit to maintain a long life assembly with minimum maintenance.
In summary, the prior art plastic impellers involve costly manufacturing procedures which involve costly equipment and various procedures or the cost of forming separate components with separate bonding of the separately bonded areas present areas of possible failure and should provide seal cooling means. The present systems do not therefore provide a structure which permits the manufacture of a relatively simple structure for controlling the volume of water flow and efficient seal cooling.
The present invention provides a one-piece impeller design including an in-place molded shroud, which may be formed with known injection molding apparatus, thereby permitting a particularly cost-effective impeller. The molded impeller is readily constructed with a proper height and vane curvature to produce a specified flow, in combination with a shroud and flow control constructed to create proper cooling of a pump seal. The single piece impeller provides a more optimum flow of the coolant around the mechanical seat of the impeller. The result is a reduction in the operating temperature of the pump seals, with an increased operating life of the seal and the pump.
More particularly, the impeller of the present invention includes a single piece impeller including a central shaft mounting hub and impeller vanes integrally formed on the periphery of the hub. The hub includes a base portion projecting outward between the vanes and functioning in combination with an integral shroud secured to the outer edges of the vanes. The shroud extends from an inner portion overlying the outer peripheral portion of the hub base portion and then outwardly to the outer edge of the vanes. The impeller is mounted to the housing having a base and an outer housing cover. A shaft and seal assembly is secured within the base with the impeller hub secured to the shaft and with the seal unit adjacent the hub. The housing base has a coolant chamber about the seal unit which projects radially beneath the impeller and in spaced relation to the hub base portion. The housing is closed by an outer cover including an outlet passageway aligned with the outlet or discharge openings defined by the radial outer ends of the vanes and the adjacent opposed wall of the housing base. The overlapping portions of the hub base portion and the shroud direct part of the flow into the cooling gap and chamber beneath the hub base portion and the housing base portion. The flow into the cooling chamber circulates through the cooling area and back to the vane passageway to the exit opening from the vanes into the coolant outlet passageway.
In summary, the present invention thus provides a one-piece molded pump impeller having a central rotating hub unit and an outer shroud connected by a plurality of vanes defining a multiple coolant flow forming part of and directed to a common discharge or outlet passageway, with a portion of the flow circulated about a seal coolant chamber about the seal unit and to the backside of the rotating hub.
The impeller of the present invention is readily injection molded with well known injection molding equipment and with conventional plastics presently used in coolant pump impellers. The impeller of the present invention produces a highly cost-effective structure with both manufacturing and assembly costs, as well as an improved and long life pump assembly.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.